1. Field of the Invention
The present invention relates to pressure sensing devices, especially for tire pressure monitoring systems, and in particular to the amplification of audio signals within tire pressure sensing devices.
2. Description of the Prior Art
A typical tire pressure monitoring (TPM) system includes a wheel-mounted unit having a pressure sensor for measuring the fluid pressure within the tire and producing an electrical signal indicative of the measured pressure. The unit also includes signal processing circuitry for processing the output signal of the pressure sensor. The output signal of the pressure sensor usually requires amplification, especially in situations where it is desired to detect relatively low amplitude components of the pressure sensor signal. In addition, the pressure sensor signal may need to be filtered. To these ends, the pressure sensor signal processing circuitry typically includes electronic amplification and filtering circuitry.
Space, weight and power consumption are important considerations in the design of the wheel-mounted unit of a TPM system and so it is desirable to simplify the signal processing circuitry. In addition, as a result of signal noise, the electronic amplification of the pressure sensor output signal can be unsatisfactory when trying to detect relatively low amplitude components of the signal.